At 10:32 PM 1/25/2003 -0500, you wrote:
>The unit operated at 220V should use about half of the power used by an 110V
>unit.  You'll save on electricity.

You will save, but not by half.  220V will use half the amps as 110V.  But
the total power use V*A is basically the same.  However you will save some
because reduction in loss due to resistance in the wires from the meter to
the heater.  It is a direct function of current and resistance.  So bigger
wire and less current means less loss even though it's the same amount of
energy.  This is why power transmission lines are high voltage.  (Low
voltage, high current has the same power but more losses than high voltage,
low current)

Example:
Assuming 2Amps @110V (220 Watts), and 1000' of 12 gage copper wire:
(12 gage copper wire being 1.588 ohms per 1000')
Power Loss along the wire is I*I*R = 2*2*1.588
Loss is approximately: 6 Watts

Assuming an equivalent power 1Amp @220V (220 Watts)
Loss is approximately: 3 Watts

Not terribly significant unless your current is high, wire is small or the
length is long.
Note that this loss is in heat.  Using too small a wire (higher resistance)
has more
loss (heat) and can start a fire.

Power loss in the device itself should be the same between the two units
because the power loss is in heat, which is exactly what you want.

Now if we were talking motors it would be a bit different,  you would also
save a bit more due to reduction in resistance loss in the device.  And
3-phase is completely different (for motors, not resistance loss).

-Tim